Proximity detectors such as touch sensitive displays are commonly used in portable electronic apparatus such as tablet computers and smart phones.
Such proximity detectors typically operate in a high definition mode where they are used to disambiguate between numerous different high definition user actuations.
If one draws an analogy between proximity detection and displaying text characters, then when proximity detectors operate in a high definition mode that is the equivalent of using a small font size. Each sensor-element occupies a small area and there are a large number of sensor elements per unit area.